This invention relates to methods of immobilizing formaldehyde contained in foamed urea formaldehyde insulation or in composite panel structures built up with a cellulosic material bound together by formaldehyde containing binders.
This invention further relates to a method of in situ treatment of structures containing foamed-in-place urea formaldehyde insulation to immobilize and react the residual formaldehyde contained in the insulation structure, thereby preventing the gradual release to the atmosphere of formaldehyde.
The construction industry has recently become acutely aware of the potential health hazzards due to free formaldehyde being present in the ambient air of homes and other structures using products that contain urea formaldehyde resin material or formaldehyde containing binder resins. A need exists to counteract the presence of free formaldehyde, in both newly manufactured construction materials and in those materials already installed in homes and other structures, including primarily the foamed-in-place urea formaldehyde insulation. Much effort has been expended by manufacturers and builders toward developing reductions in formaldehyde levels in existing housing units as an interim solution to the formaldehyde problem in existing dwellings.
It is well known that ammonia, as an active chemical ingredient has a natural chemical affinity for reacting with formaldehyde to form a compound called hexamethylene tetramine. This is a stable white chrystalline organic material formed as a product of a reaction of the two gases in such a way as to immobilize formaldehyde. A prior development known to this inventor was the treatment of a mobile home using ammonia vapor that had been evaporated from a concentrated ammonium hydroxide solution placed in buckets on the floor of the various rooms of the mobile home. The mobile home was closed up in an effort to keep the ammonia vapors inside and the system allowed to generate those vapors of ammonia for a period of approximately 24 hours, in an attempt to neutralize the formaldehyde vapors in that home. The result of that first test, and a substantial number of mobile homes treated subsequently had indicated that this ammonia evaporation technique would substantially reduce the residual formaldehyde vapor levels. In the case of this specific mobile home unit treated as described above that unit has since been monitored on a quarterly basis and has been found to have a permanently reduced level of formaldehyde vapors within the home.
Ammonia gas vapors, being rather large molecules, suffer from a difficulty in penetrating and flowing through tortuous pathways such as is frequently found in the wall construction of dwellings. As a result, the interior exposure only of the walls in a mobile home or residence to ammonia vapors alone fails to reach all areas of the wall structure containing free formaldehyde. The prior art process was primarily directed to treating wood product paneling and fabrics bonded together with urea formaldehyde resins, and is ineffective in treatment of urea formaldehyde foamed in place insulation in many dwellings.
In considering methods of treating stud wall structures with anhydrous ammonia as the active ingredient, a number of potential barriers to accomplishing this were encountered: (1) Current code requirements for fire blocking and/or cross bracing within the stud cavities of walls could potentially provide a barrier for injecting of an active neutralizing gas such as anhydrous ammonia. (2) It also became important to consider whether the individual bubbles that made up the urea formaldehyde foam were of a closed cell or an partially open cell structure to allow for the entry of the active neutralizing gas into the foam system.
Steps taken by others in the past to reduce formaldehyde emission from urea formaldehyde resins and foams include the incorporation of an aromatic substance into the prepolymer which reacts with the free formaldehyde after polymerization, for example as is shown in U.S. Pat. No. 4,273,883 issued June 16, 1981 to Korf. Starch and excess urea have similarly been used as shown in U.S. Pat. No 4,119,757 issued Oct. 10, 1978 to Hobson, U.S. Pat. No. 3,996,190 issued Dec. 7, 1976 to O'Neill, and U.S. Pat. No. 3,231,525 issued Jan. 25, 1966 to Kelly, et al. Ammonium bicarbonate and carbonate, with a terpene also is taught as constituents to be added before polymerization of the foam to decrease formaldehyde emissions in U.S. Pat. No. 3,312,639 issued Apr. 4, 1967 to Justice.
All of the foregoing treatment schemes must be carried out during processing of the ingredients of the polymerization system. No teaching shows post treatment other than the crude exposure, room by room, to ammonia fumes as described above.